Axial piston pump with pre-compression volume(PCV)has lower flow ripple in large scale of operating condition than the traditional one.However,there is lack of precise simulation model of the axial piston pump with PCV,so the parameters of PCV are difficult to be determined.A finite element simulation model for piston pump with PCV is built by considering the piston movement,the fluid characteristic(including fluid compressibility and viscosity)and the leakage flow rate.Then a test of the pump flow ripple called the secondary source method is implemented to validate the simulation model.Thirdly,by comparing results among the simulation results,test results and results from other publications at the same operating condition,the simulation model is validated and used in optimizing the axial piston pump with PCV.According to the pump flow ripples obtained by the simulation model with different PCV parameters,the flow ripple is the smallest when the PCV angle is 13°,the PCV volume is 1.3′10–4m3at such operating condition that the pump suction pressure is 2 MPa,the pump delivery pressure 15 MPa,the pump speed 1 000 r/min,the swash plate angle 13°.At the same time,the flow ripple can be reduced when the pump suction pressure is 2 MPa,the pump delivery pressure is 5 MPa,15 MPa,22MPa,pump speed is 400 r/min,1 000 r/min,1 500 r/min,the swash plate angle is 11°,13°,15°and 17°,respectively.The finite element simulation model proposed provides a method for optimizing the PCV structure and guiding for designing a quieter axial piston pump.
Improving the carrying ability of oil film between slipper and swash plate and reducing the partial abrasion of slipper are important to improve the service life and reliability of axial piston pump.In this paper,a numerical simulation model was developed for slipper/swash-plate friction pair based on the elastohydrodynamic theory.The dynamic micro-motion and pressure distribution of slipper were analyzed and it was pointed out that the tilt of slipper was the main reason for its partial abrasion.The simulations about the slippers with different slopes on the outer edge of the sealing belt showed that the partial abrasion could reduce the carrying ability and increase the leakage of the slipper/swash-plate pair.The proper slope on the inner edge helped to improve the carrying ability and reduce the leakage of slipper.The experimental tests were in accord with the simulation results to a great extent,showing that the simulation model had a high accuracy and could be applied to the design and optimization of slipper,and that the slipper with optimal inner slope provided an encouraging method to improve the efficiency and reliability of axial piston pump.
The limit working parameters and service life of axial piston pump are determined by the carrying ability and lubrication characteristic of its key friction pairs. Therefore, the design and optimization of the key friction pairs are always a key and difficult problem in the research on axial piston pump. In the traditional research on piston/cylinder pair, the assembly relationship of piston and cylinder bore is simplified into ideal cylindrical pair, which can not be used to analyze the influences of radial micro-motion of piston on the distribution characteristics of oil-film thickness and pressure in details. In this paper, based on the lubrication theory of the oil film, a numerical simulation model is built, taking the influences of roughness, elastic deformation of piston and pressure-viscosity effect into consideration. With the simulation model, the dynamic characteristics of the radial micro-motion and pressure distribution are analyzed, and the relationships between radial micro-motion and carrying ability, lubrication condition, and abrasion are discussed. Furthermore, a model pump for pressure distribution measurement of oil film between piston and cylinder bore is designed. The comparison of simulation and experimental results of pressure distribution shows that the simulation model has high accuracy. The experiment and simulation results demonstrate that the pressure distribution has peak values that are much higher than the boundary pressure in the piston chamber due to the radial micro-motion, and the abrasion of piston takes place mainly on the hand close to piston ball. In addition, improvement of manufacturing roundness and straightness of piston and cylinder bore is helpful to improve the carrying ability of piston/cylinder pair. The proposed research provides references for designing piston/cylinder pair, and helps to prolong the service life of axial piston pump.
